This invention relates to a computer system, a management method, and a server. More particularly, this invention relates to a computer system that manages a PCI switch.
In recent years, blade servers which include a plurality of computers in a single machine have been put into use in order to facilitate server management. Further, improvement in processing performance of CPUs brought about by a multi-core technology, which gives a CPU a plurality of processor cores, has led to widespread use of a virtual server technology, which uses a CPU efficiently by running a plurality of virtual servers on a single computer.
While the CPU performance has improved, there has been a shortage of I/O devices which require connectors and ports for input and output. The shortage of I/O devices can be improved by enhancing the extensibility and flexibility of I/O devices with the use of a PCI switch technology.
Hot-plug is a technology known to enhance the flexibility of I/O devices by dynamically changing the I/O device configuration after the server is booted up. The PCI Express standard defined by the PCI-SIG lays down the register specifications and the like of hot-plug controllers which control hot-plug. Any OS that supports PCI Express hot-plug can employ hot-plug irrespective of the type of I/O devices.
If a pseudo device is prepared within a PCI switch in anticipation of the future use of PCI hot-plug and a resource for an I/O device is reserved upon booting up of the server, the mechanism of hot-plug can be utilized when the I/O device is actually added to reconfigure the I/O device configuration dynamically as described in, for example, JP 2008-046722 A.
The PCI-SIG also defines a multi-root PCI switch technology, which extends a PCI switch used by a conventional single server such that a plurality of computers are connected to a plurality of peripheral component interconnect (PCI) devices (or PCIe(xpress) devices) which are I/O devices as described in, for example, an online document “Multi-Root I/O Virtualization and Sharing Specification Revision 1.0” published by PCI-SIG in May 2008 and retrieved on Jan. 6, 2009 at PCI-SIG web site, http:// . . . /specifications/iov/multi-root/.